CONTROL OF DEFECTS IN THE HETEROEPITAXIAL GROWTH OF GAAS ON SILICON

In this paper we present the results of a study of the approaches we have adopted to limit defect propagation in GaAs on silicon. These include use of SLS, thermal annealing, and restricted area growth. We have demonstrated that bands of GalnAs/GaAs Strained Layer Superlattice (SLS), or single ternary layers can be used to intercept and bend over dislocations. However, although this approach can lead to significant reductions in defect density 10-9 to 10-7 cm-2, the effect is limited due to interactions between dislocations that have been successfully diverted and the consequent reduction of the strain field at the SLS/matrix interface. Dislocation density reductions from 10-8 to 10-6 cm-2 were observed for restricted area deposition of GaAs on profiled silicon substrates. The objective here was to provide 'sinks' to pin dislocations at exposed areas or at specific crystal facets defined by the substrate geometry. Sequential thermal anneal/grow routines were also investigated both separately, and in conjunction with other defect limiting techniques such as the use of the strained layer superlattices and growth on profiled substrates. These structures were assessed by X-ray diffraction, plan view, and cross-sectional TEM. Where appropriate, experimental GaAs/Si device structures were also fabricated and tested. © 1990.